Hydraulic system



United States Patent Inventor Katsuhiko Iliima Ohta-ku, Tokyo, Japan Appl. No. 774,679 Filed Nov. 12, 1968 Patented Dec. 1, 1970 Assignee Mitsubishi Jukogyo Kabushiki Kaisha Tokyo, Japan Priority Nov. 24, 1967 Japan No. 42/75299 HYDRAULIC SYSTEM 4 Claims, 9 Drawing Figs.

US. Cl 91/414, 60/52 Int. Cl ..F15b 11/00, 1 F 1 5b 15/ 1 8 [50] Field ofSearch 91/411, 414; 60/52(H.E.)

[5 6] References Cited UNITED STATES PATENTS 3,363,516 l/1968 Hubbard 60/52H.E.X

Primary Examiner-Edgar V. Geoghehan Attorney-McGlew and Toren ABSTRACT: Hydraulic apparatus includes plural hydraulic actuators and a hydraulic control circuit therefor. The control circuit has a single source of hydraulic fluid under pressure, such as a pump, and plural directional control valves each controlling operation of a respective actuator. A flow divider valve is connected in the control circuit and distributes the hydraulic fluid in accordance with the requirements of the respective actuators.

Patel fled Dec. 1, 1970.

Sheet ATTORNEYS Patented Dec. 1, 1970 3,543,646

"Sheet 6 of 7 :5 FIG] (AWE/V70)? Kqtsuhlko lijimo y ATTORNEYS HYDRAULIC SYSTEM BACKGROUND OF THE INVENTION The present invention is directed to hydraulically operated apparatus used for operating hydraulic machines such as, for example, power shovels, back hoes, fork lift trucks, bulldozers, and the like.

One conventional hydraulic circuit used in such machines is shown in FIG. 1. Hydraulic fluid is drawn from a reservoir (not shown) and flows through a strainer l to a single pump 2. The output of pump 2 is connected to a pressure relief valve 3 and is supplied to directional changeover or control valves 4 -4., connected in parallel with each other. The return flow from valves 4 -4., passes through a filter 5 connected in parallel with a pressure relief valve 6 and flows back to the reservoir.

The directional control valves 4 -4., are connected in controlling relation with hydraulic actuators 7, 8, 9 and 10, respectively. Of these hydraulic actuators, hydraulic actuator 7 is a rotary actuator, hydraulic actuator 8 is a bucket actuator, hydraulic actuator 9 is an arm actuator and hydraulic actuator I0 is a boom actuator. All of the actuators 7l0 are operated by hydraulic fluid under pressure supplied through the respective control valves.

In the case of simultaneously operating a plurality of the directional control valves in a hydraulic circuit as shown in FIG. 1, the lightest load, for example, the load on the control valve 4, controlling the rotating motor 7, is actuated first, and it is practically impossible to actuate more than two loads at the same time. More particularly, the amount of hydraulic fluid under pressure required for the motor 7, in a conventional power shovel or back hoe, due to the angular velocity thereof is smaller than that required for other actuators, such as the bucket actuator 8, the arm actuator 9 and the boom actuator 10. For this reason, a flow rate controlling valve 11 is interposed between control valve 4, and motor 7 to control the quantity of hydraulic fluid supplied to motor 7. A pair of pressure relief valves 12 are also provided in the lines connecting motor 7 to valve 4 In order to prevent the hydraulic actuator of the lighter load, such as the rotating motor 7, from being first operated, and in order to permit simultaneous operation of two hydraulic actuators irrespective of the size of the load, there is also known another circuit arrangement such as shown in FIG. 2. In the circuit arrangement of FIG. 2, the hydraulic actuators 7, 8, 9 and It are supplied with hydraulic fluid under pressure by two or more pumps 2 and 13. However, with the arrangement of FIG. 2, it is necessary to let the sum of the maximum input power of the pumps 2 and 13 coincide with the output power of the driving engine. Although there will be no problem when both pumps 2 and 13 are used simultaneously, it is impossible to use effectively the output power of the driving engine when a single pump 2 or 13 is operated by itself. Furthermore, since a plurality of pumps are necessary, the structure is complicated with a resultant increase in cost. Also, since the amount of hydraulic fluid required for blade control of a bulldozer or tilt control of a fork lift is smaller than that required for lifting, a plurality of flow rate controlling valves are used, and this further increases the cost.

SUMMARY OF THE INVENTION This invention relates to hydraulically operated apparatus having a plural hydraulic actuators and, more particularly, to such apparatus including a novel flow divider valve connected in a hydraulic control circuit to distribute the working fluid in accordance with the respective outputs of the actuators.

In accordance with the invention, the flow divider valve is connected in the flow control circuit in series with the direction changeover or control valves and at such a location that it is immediately in advance or upstream of a first control valve controlling the flow to the lightest loaded actuator. In the neutral position of this first control valve, the pressure fluid inlet of the dividervalve is connected to a bypass flow passage in the first control valve and, through the bypass flow passages of the succeeding valves, to the fluid return line leading to the hydraulic fluid reservoir. Under these conditions, when any control valve other than the first control valve is operated, the full flow of hydraulic fluid under pressure is available to operate its controlled actuator. However, when the first control valve, controlling the lightest loaded actuator is operated, the flow from the inlet of the fluid divider valve to the bypass passage of the first control valve is blocked. The fluid divider valve, under these circumstances, delivers a part, such as half, of the total available hydraulic fluid under pres sure to the hydraulic actuator controlled by the first valve, and supplies the remainder of the available hydraulic fluid under pressure to the other control valves succeeding the first control valve.

An object of the present invention is to provide a hydraulically operated apparatus which is simple in construction and low in cost.

Another object of the invention is to provide such a hydraulic apparatus in which a pressure compensating flow rate divider valve is operatively associated with plural control valves arranged in parallel.

A further object of the invention is to provide such a flow rate divider valve in a hydraulic machine, such as a power shovel, or back hoe, and in such a manner that a portion of such a machine, which is operable by a rotary actuator, always has half the discharge from a pump, in the hydraulic control circuit, supplied to its actuator.

Another object of the invention is to provide such a hydraulic apparatus in which simultaneous operation of other acmators, at the time or rotation of a part of the machine, is possible.

A further object of the invention is to provide such a hydraulic apparatus in which, when a rotary motor thereof is not being actuated, the full available quantity of hydraulic fluid under pressure is supplied to every other actuator.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIGS. l and 2 are schematic flow diagrams of the hydraulic circuits of conventional apparatus, as mentioned above;

FIG. 3 is a somewhat schematic flow diagram, with some parts shown in section, of one form of hydraulic apparatus embodying the invention;

FIGS. 4, 5 and 6 are views, similar to FIG. 1, illustrating the operation of the apparatus shown in FIG. 3;

FIG. 7 is a view, similar to FIGS. 1 and 2, but illustrating the embodiment of the invention shown in FIGS. 3-6;

FIG. 8 is a view, similar to FIG. 3, illustrating a second embodiment of the invention; and

FIG. 9 is a view, similar to FIG. 3, but illustrating a third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 3, hydraulic apparatus embodying the invention is illustrated as including a hydraulic fluid reservoir 21 containing a quantity of hydraulic fluid 22 and having a filter 23 interposed at a port connected to a suction line 24 leading to the inlet of a pump 25 having a pressure relief valve 26 connected in parallel therewith to regulate the pressure in the hydraulic control circuit. The outlet port of pump 25 and the corresponding outlet port of pressure relief valve 26 are conjointly connected to a supply line 2'7 leading to a pressure compensating flow divider valve 29 in a housing 28. Valve housing 28 also contains directional changeover or control valves, such as the four control valves 29 -29,. Each control valve includes a slidable spool valve member 30 -30,, respectively. Each spool valve member comprises a valve stem or shaft 32 -32 having pistons secured coaxially thereto in aximasses ally spaced fixed positions. The pistons are indicated at 33 -33 35 -35 and 36 -36 One end of each spool valve member is formed with a valve operating means, as indicated,

respectively, at 3il' 3i and the opposite end of each spool valve member has operatively associated therewith a respective spring 37 -37 which biases the associated spool valve member to the position shown in FIG. 3, which is the neutral position.

On opposite sides of flow divider valve 29, there are formed hydraulic fluid flow passages 38 and 39 through which the hydraulic fluid divided by valve 29 is passed. Flow passages 38 and 39 communicate with a bore 31, of flow control valve 39,, this bore slidably receiving the pistons 33 -33 of valve 30,. A flow line 41 communicates with bore 31 between pistons or piston valves 33, and 33 and a second flow line 32 communicates with bore 31, between piston valves 33 and 33 I low lines 4i and 42 are connected to respective opposite ends of the cylinder of rotating motor ill, so that a piston 43 in this cylinder is moved in opposite directions in accordance with whether fluid under pressure is supplied to line 41 or to line 32. The motor 40 is a rack and pinion-type rotatable motor, including a pinion rotated by a rack forming part of piston 43.

A passage 44 connects flow passage 38 to bore 3% of control valve 3%, controlling operation of a hydraulic actuator including a cylinder 57 containing a piston 36 connected to bucket 45. Supply of fluid to cylinder 47, and return of fluid therefrom, are effected by lines 48 and 49. Line is connected to bore Bl: between piston valves 34, and 34 and line 49 is connected to bore Bi between piston valves 34 and 34,.

Hydraulic fluid flow passages 44,, 44 and 44 are trifurcated from flow passage 44 and communicate with a bore 31 of control valve 30 Lines 56 and 51 are connected to compartments in bore 31 defined, respectively, by piston valves 35, and 35 and piston valves 35;, and 35 Lines d and 51 serve as hydraulic fluid supply and return lines for a cylinder 54 having reciprocable therein a piston 53 connected to a boom 52. Cylinder 54 is pivotally connected to a rotatable pillar 55, as is also the inner end of boom 52. The outer end of boom 52 has pivotally connected thereto an arm 56 carrying the cylinder 47.

The trifurcated flow passages 44 id-' and id' extend from bore 31 of control valve Bill to bore 3i, of control valve 30,. Flow lines 59 and 6b communicate with bore 31,, between piston valves 36, and 336 and piston valves 36;, and 36 respectively. Lines 59 and 6b are connected to a cylinder 58 housing a piston 57, the inner end of cylinder 58 being pivotally connected to boom 52 and the piston rod of piston 57 being pivotaily connected to arm 56. A return line at is connected to bore 31 and return lines 62 and 63 communicate with opposite ends of bores 31 -31,, passages 62 and 63 being interconnected with return line 61. Return line 61 is connected to reservoir 22 througha filter 64%.

Referring now to the operation of the apparatus, the pump 25, which is driven by a prime mover, draws hydraulic fluid from reservoir 21 through filter 23 and line 24 and delivers the hydraulic fluid, under pressure, to the supply line 27. if the spool valves 30,-3ih are all in the neutral position as shown in HQ. 3, the hydraulic fluid flows through passage 29' around the central periphery of flow divider valve 29, and then flows through a bypass circuit formed by passages 44, 44 4W and 61 to filter M from which'the flow returns to reservoir 21.

Referring to H0. 4, when spool valve 36), is depressed against the force of return spring 37,, passage 29' is blocked from passage Fill by piston valve 33 The hydraulic fluid under pressure in supply line 27 is then forced to flow into the free piston of flow divider valve 29, from where the hydraulic fluid is divided between passages 38 and 39 at a fixed proportion irrespective of the pressure. The flow rates into the respective passages 38 and 39 are determined by the areas of the orifices at opposite ends of the flow divider valve 29.

That portion of the hydraulic fluid flowing into the passage 39 is directed through line 4 to actuator ell-43 in a such as to rotate this actuator counterclockwise. The portion of the hydraulic fluid entering passage 3% is bypassed, through passages 44 4 2", and 611 to reservoir 21 through iiltcr Thereby, only a reduced amount of the hydraulic fluid adapted to the required angular velocity of motor i delivered to motor 40. In the event spool valve 3%, is pulle out in the opposite direction, motor 4% is rotated ClOCltWIe but otherwise the flow conditions are as described above. this latter case, the fluid under pressure flows through line 42 and returns through line 41 whereas, during counterclockwise rotation of motor 40, the fluid is supplied through line 61 and .is returned through line s2.

Referring now to H6. 5, if spool valve MP is moved to the right, from its neutral position in FIG. 3, hydraulic fluid under pressure from supply line 27 flows through passage 29 to passage 44 independently of flow divider valve 29. The passage 4 and line 4% are now in communication with each other so that the fluid under pressure is delivered to actuator 46-47 to extend piston 46 connected to bucket 45. if spool valve 3% is moved to left from the neutral position, piston 46 is retracted. in either case, the entire amount of hydraulic fluid under pressure supplied from pipe 25 is supplied to cylinder 47.

The same holds true upon operation of the spool valves 3G and 3th, the entire available amount of hydraulic fluid under pressure, from pump 25, being supplied to the cylinders 54- or 58 to operate boom 22 or arm 56, respectively. The operat on takes place in the same manner as described for the operation of spool valves 30, and fiil W hen both spool valves 3% and 3% are operated simultaneously from the neutral position, as shown in FlG. 6, passage 29 is blocked from passage M by piston valve 33 and passage 44 is blocked from passage 4% by piston valve 34 The hydraulic fluid under pressure in supply line 27 flows into the free piston of flow divider; valve 29 and is divided between the passages 38 and 39. That portion of the hydraulic fluid entering passage 39 is effective to rotate motor 4i). The other portion of the hydraulic fluid, entering the passage 38, flows through passage &4 into line 38 to enter cylinder 47 to extend piston 56.

Thus, flow divider valve 2& divides the flow of hydraulic fluid under pressure always at a fixed rate and irrespective of the magnitude of the load on rotating motor dill or on cylinder 47, so that these two actuators can be operated simultaneously. Similarly, in the case of simultaneous operation of spool valve 30, and spool valve 30 or 30 both the rotating motor 44) and the actuators 54 or 58 are operated simultaneously and without any time lag. It will be noted that, in H68. 4, 5 and e, parts corresponding to those shown in FIG. 3 have been designated with the same reference numerals, so that further explanation is believed unnecessary.

FIG. 7 is a flow circuit diagram corresponding to FIG. 2 with corresponding parts being given the same reference characters so that further explanation of FIG. 7 is believed unnecessary.

From the foregoing, it will be understood that, in the embodiment of the present invention just described, flow divider valve 29 is actuated only when a rotary operation is to be performed, such as angular displacement of a power shovel or the like in traverse. The apparatus just described, while involving a pump system, provides for simultaneous operation of other actuators during operation of rotating actuator. it also provides for supplying hydraulic fluid to the rotating motor 40 in a volume adapted to the required angular velocity of the latter. in addition, since the flow rate for effecting rotation is controlled by flow divider valve 29, the heat balance is improved as compared with conventional devices in which the flow rate is controlled by an orifice or other similar means.

in the conventional two-pump system, such as shown in FIG. 2, the sum of the maximum input power of the two pumps must be correlated with the output power of the prime mover, so that discharge from one pump is reduced and, when only one pump is operated, the operating speed is reduced resulting in poor working performance. By comparison, in the apparatus so far described, the entire available amount of hydraulic fluid under pressure is fed into each actuator except the actuator effecting angular displacement, so that a very effective operation can be attained. In turns of cost, the invention arrangement which is a one-pump system, is more advantageous than a two-pump system and the conventional multivalve construction can be improved without extensive modifications. Thus, apparatus as described can be constructed at a relatively small cost.

In a second embodiment of the invention, as shown in FIG. a, spool valves 3% and 30., are omitted. Valve 30, controls operation of a tilt cylinder 70 having a piston 71 therein, and valve 30 controls operation of a lift cylinder 74 provided with the piston 75. For this purpose, lines 41 and 42 connect cylinder 70 to valve 30,, and lines 48 and 49 connect cylinder 74 to valve 30 The free end of piston 71 is pivotally connected to an inner member 73 of a pair of telescoped members including an outer member 72. One end of lift cylinder 74 is pivotally connected to the base of inner member 73, and the free end of piston 75 is pivotally connected to the outer end of telescope member 72. A fork 76 is secured to project from outer telescoped member 72. For the parts of the hydraulic control system, the same reference characters have been used as in the embodiment shown in FIGS. 3 through 6.

With respect to the operation of the embodiment shown in FIG. 8, the latter operates in the same manner as does the embodiment shown in FIGS. 3 through 6. When valve 30 is operated to actuate cylinder 70 and piston 71, hydraulic fluid under pressure in passage 27 enters the free piston of flow divider valve 29 and is divided at fixed and proportionate rates between passages 38 an 39 independently of the pressure. That portion of the hydraulic fluid delivered to passage 39 is delivered to tilt cylinder 70 to effect movement of piston 71, whereas the portion of the hydraulic fluid delivered to passage 38, assuming a rightward displacement of valve operating member 3W is delivered to the bypass passages for return to reservoir 21.

if valve 3% is operated with valve 39, remaining in the neutral position, the flow divider valve 29 is not effective, and all the hydraulic fluid under pressure flowing through supply line 27 is delivered to lift cylinder 74 to operate its piston 75. When valves 30, and 30 are operated simultaneously, the hydraulic fluid under pressure enters the free piston of the flow divider valve 29 and is divided between passages 33 and 39 at a fixed proportion irrespective of the pressure used. The thus divided hydraulic fluid portions are delivered, respective ly, to lift cylinder 74 and tilt cylinder 70.

Consequently, with this second embodiment of the invention, the operational inconveniences of conventional devices, due to the impossibility of effecting simultaneously tilting and lifting operations, are overcome. There is no need to provide an orifice flow rate controlling valve or similar means, such as has been used conventionally for regulating the tilting rate. The pressure loss is reduced and the heat balance is improved, as compared with a conventional orifice flow rate controlling system.

FIG. 9 illustrates a third embodiment of the invention as applied to the hydraulic circuit of the blade of a bulldozer. In this case, also, the valves 30;, and 30., have been omitted. Lines dll and 42 connect valve 30 to the cylinder flll for operating a piston 83 associated with the blade 85. Lines lb and 49 connect valve 30 to a cylinder 82 for operating a piston 84 connected to a support for blade 85. The hydraulic actuators are interconnected with the chassis of the bulldozer and with the parts to be moved, so that operation of the system is effected in the same manner as described for FIG. 8. As the same references characters used in FIGS. 3-6 and 8 are used in FIG. 9, it is believed that the operation of the parts will be clear.

In the embodiment of FIG. 9, flow divider valve 29 is arranged in advance or upstream of the first stage control valve 30 but it should be understood that flow divider valve 29 could be arranged between the stages represented by the spool control valves 30, and 30 Alternatively, in the arrangement described with reference to FIGS. 3 through 6, flow divider valve 29 could be arranged between any two of the flow control valves 3tl 3tl The hydraulic lines connecting the control valves to the respective actuators can be changed in accordance with the particular applications.

From the foregoing description, it will be understood that, with the present invention, hydraulic fluid under pressure from a single pump is supplied simultaneously to a plurality of hydraulic actuators through respective directional changeover or control valves and that it is only when a certain one of the control valves is actuated that hydraulic fluid under pressure is permitted to enter the pressure compensating, flow divider valve for division thereby. As a result, a rotatable portion of the machine, operated by a rotary actuator, can always be supplied with half the output of the single hydraulic pump, so that acceleration of the angular velocity, which was an inherent defect of prior art one-pump systems, is absolutely inhibited.

In addition, other actuators may be operated simultaneously with the rotary actuator and, when the rotary actuator is not actuated, the entire output of the single pump is supplied to the other actuators so that time delays in their operation are prevented. The structure of the apparatus is greatly simplified with the resultant reduction of cost. The arrangement of the invention thus provides an extremely effective hydraulically operated apparatus which can be used in various types of hydraulic machines, such as power shovels, back hoes, bulldozers, forklifts and the like.

lclaim:

1. In hydraulically operated apparatus having plural hydraulic actuators and a hydraulic control circuit therefor including a single source of hydraulic fluid under pressure, plural directional control valves each controlling operation of a respective actuator, a supply line connecting the high pressure side of the single source to the control valves and a return line connecting the controlvalves to the low pressure side of the single source: the improvement comprising, in combination, each of said control valves having a bypass flow passage connected to said return line and opened in the neutral position of the associated control valve, a pressure fluid supply inlet, supply and return ports connected to the associated actuator and a pressure fluid outlet; and a flow divider valve connected in said control circuit and having an inlet connected to the bypass flow passage of a first control valve immediately succeeding said flow divider valve in said control circuit, a first outlet connected to the pressure fluid supply inlet of said first control valve and a second outlet connected to bypass flow passage and the pressure fluid supply inlet of a second control valve immediately succeeding said first control valve in said control circuit; said flow divider valve being formed with distribution passages effective to distribute hydraulic fluid under pressure, entering said flow divider valve, in a fixed proportion, independent of pressure of the fluid, between said first control valve and the other control valves; hydraulic fluid under pressure in said supply line, when sald first control valve is in the neutral position, flowing from said supply line to the bypass flow passage of said first control valve in bypassing relation with said flow distributing valve; said first control valve, in an operated position, blocking flow from said supply line to said bypass flow passage of said first control valve whereby fluid under pressure from said supply line enters said flow divider valve for such distribution.

2. In hydraulically operated apparatus, the improvement claimed in claim 1, in which said flow divider valve is connected in said control circuit between said supply line and said directional control valves.

3. ln hydraulically operated apparatus, the improvement claimed in claim 1, in which said flow divider valve comprises a free piston mounted in a bore, said free piston being formed with said flow dividing passages and with a passage communicating with said inlet and connected to all of said flow dividing passages; said bore being formed with a passage extending peripherally around said free piston and interconnecting said inlet of said flow divider valve to the bypass flow passage of said first control valve; said bore being formed with a pair of second passages, each at a respective end of said free piston, and each communicating with a respective one of said first and second outlets as well as with a respective distributing 

